1. Field of the Invention
The present invention relates to information processing apparatuses, and more specifically relates to an information processing apparatus in which an operation unit is illuminated by using a part of backlight for illuminating, for example, a liquid crystal display device.
2. Description of the Related Art
FIGS. 1 and 2 show the construction of a known notebook personal computer (hereinafter referred to simply as a notebook PC) 1. FIG. 1 a diagram showing the external view of the notebook PC 1, and FIG. 2 is an enlarged sectional view of a part of the notebook PC 1.
The notebook PC 1 includes a flat, plate-shaped main body 11 which contains a motherboard, a hard disk drive, etc., and a thin display unit 12 which is constructed of a liquid crystal display (LCD) or the like and which is pivotally attached to the main body 11 with a hinge 13.
The display unit 12 is constructed of a liquid crystal panel 15, an external frame 16, and a backlight unit 20 which includes a cold-cathode fluorescent lamp 21, an optical waveguide 22, a diffusion sheet 23, and a reflector 24. Although not shown in the figure, the backlight unit 20 also includes a lens sheet, a reflective sheet, etc.
Light emitted from the cold-cathode fluorescent lamp 21 of the backlight unit 20 is guided upward through the optical waveguide 22, and is diffused by the diffusion sheet 23 such that the entire surface of the liquid crystal panel 15 is illuminated. In order to efficiently guide the light emitted from the cold-cathode fluorescent lamp 21 upward, the reflector 24 is disposed around cold-cathode fluorescent lamp 21 so as to cover the sides and the bottom of the cold-cathode fluorescent lamp 21.
Since the liquid crystal panel 15 is not a self-luminous device, it needs to be uniformly illuminated by the backlight unit 20 from the back.
When a user 2 uses the notebook PC 1, he or she rotates the display unit 12 away from the main body 11, so that an operation unit such as a keyboard 14 formed on the top surface of the main body 11 can be operated and the display unit 12 can be viewed. The liquid crystal panel 15 of the display unit 12 is illuminated by the backlight unit 20, and displays characters, figures, etc.
When light is emitted from the liquid crystal panel 15 of the display unit 12, that is, when light is emitted from the backlight unit 20 through the liquid crystal panel 15, the light is emitted in an approximately horizontal direction in the figure so that it is effectively guided toward the user 2.
Since the light emitted from the liquid crystal panel 15 is guided mainly toward the user 2 as described above, the user 2 can easily view the liquid crystal panel 15 which is illuminated brightly. However, when the user 2 uses the notebook PC 1 in a dark environment (for example, in a room where lights are turned off at night, in a conference room where a projector is being used, in an aircraft flying at night, etc.), the operation unit such as the keyboard 14 is placed in a dark region, as shown in FIG. 1. Therefore, it is difficult to operate the notebook PC 1 in such an environment.
Accordingly, Japanese Unexamined Patent Application Publication No. 2001-67145, for example, discloses a method for illuminating an operation unit by disposing an optical waveguide device at the lower side of a liquid crystal display to guide a part of backlight toward the operation unit.
According to the above-described publication, the optical waveguide device is placed near the operation unit at the lower side of the liquid crystal display. Thus, the optical waveguide device obstructs the movement of the user when the user operates the operation unit. In addition, light emitted from the optical waveguide device tends to enter the user's eyes directly. Therefore, the operability of the operation unit is degraded.
In addition, it is difficult to uniformly illuminate the operation unit by the light emitted from the optical waveguide device.